Don,
Do not loose your heart. I think you need a bit more practice in verbal with a strategic approach. Go through all your previous tests (if you have documented them) and find out your weak ares. If your have performed poor in SC then go throught
MGMAT SC guide diligently and try to digest all those rules of grammar. For CR go through the Powerscore CR bible and GMAT CR questions will be cakewalk for you. And for RC you need only practice. Your math score is awesome.
Another point, You might be lacking endurance or stamina for the whole 4 hr test. This is an indicator of several previous test takers who did well in quant and verbal ( doing in piecemeal during practice test at home) but after 2 hrs into the real GMAT test they can not really focus on verbal ultimately yielding lower verbal score.
So please evaluate your position and charge with full enthusiasm. You can do it.
good luck